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The resolution of water-in-crude oil (W/O) emulsions formed during extraction or desalinaton processes of crude oil is still a problem for the oil industry. Among the main separation processes used today, electrostatic separation induced by the application of DC or AC electric fields is the most interesting because it is ecologically correct. However, the electroseparation efficiency is still limited by the current lack of knowledge concerning the mechanism that is behind this process. Stabilization of the water/crude oil emulsion is guaranteed, mainly, by resins and asphaltenes that are present at the W/O interface, forming a rigid cross-linked film that wraps the droplets. The influence of salts and the salinity of the aqueous phase on the stability of emulsions is poorly known because most researchers use, as the aqueous phase, a complex saline solution composed of a mixture of chlorides and sulfates of mono- and divalent cations to simulate the composition of seawater. Thus, the isolated effect of each type of cation may not be known. In this work, we used the rheology technique to study the effect of cation type and salinity of the aqueous phase on the stability of water/oil emulsions, under application of a DC electric field. It was verified that the stability of the emulsions follow this order: H2O ≪ Na+ ∼ K+ < Ba2+. It was also observed that the presence of salts increases the stability of the emulsions up to a critical value of ionic strength (∼0.1–0.3 mol L–1, depending on the system), above which the stability decreases, tending to that observed for the emulsion produced with water.

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A simple commercial blood glucose meter is used to follow the kinetics of mutarotation of D-glucose in aqueous solution. The results may be compared with those obtained using an automatic polarimeter, if this is available This experiment is proposed for use by students in a general chemistry, biology, organic chemistry, and physical chemistry laboratory at the college level. It can also be used as an alternative technique to the classical methods that use relatively expensive equipment, which are not always accessible to students. The technique of indirect measurement of the kinetics of mutarotation of D-glucose through an enzymatic redox reaction also provides an example of the chemical and kinetic approaches to the mutarotation phenomenon and the principle of enzymatic stereospecificity. The test strips of the blood glucose meter contain glucose dehydrogenase, an enzyme specific for the anomer of D-glucose in solution.